So I watched this video today and a lightbulb came on.
I noticed that when I walk forward, I walk forward with the disc. During the X-step I reach back by bringing the disc back. In the video, there they kinda hold the disc in the place it started and use the X-step to walk past it. Thus, at the end of the step X-step the disc is already behind you and your arm is extended.

It's like you don't actually "reach back" (verb) so much as you end up in a reach back position. This would explain why the X-step never did much for me and why my timing is off when I try to reach back too far. Can someone tell me if I'm right about this?

Well, I didn't find 40 feet but I did throw three drives about as far as I've thrown them and I could tell I was overall throwing harder. I threw two drives where I knew I didn't quite get all of it and put a little too much air under them-- and they still went farther than my regular drive and faded much less than I thought they would.

Problem was, I kept getting too excited and screwing up my form. I nailed about twice the number of trees I usally do-- but hey, I nailed them really hard.